Study: Broodmares on Pasture Don't Always Need Grain

Although both groups of mares spent exactly the same amount of time grazing (15 hours a day on average), pasture-only mares ingested 12% more grass during the entire study period than the complementary feed group.

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Horse owners are continually looking for ways to reduce feed costs without disturbing their horses' health, and a group of French equine nutritionists have some good news in this department: According to recent study results, lactating saddle horse mares on good quality pasture didn’t need to be fed grain to maintain their weight or their foals’ growth.

“Not complementing equine diets with feed would represent a double benefit to horse breeders, on an economic and environmental level,” said Claire Collas, PhD, researcher at French National Institute for Agricultural Research (INRA) in Saint-Genès-Champanelle. Collas presented her work at the 2013 French Equine Research Day, held Feb. 28 in Paris.

In Collas’ study, 16 riding horse broodmares grazed pastures with their nursing foals for four months. During this time, eight of the mares received complementary barley feed daily (60% of energy requirements for lactation), and the other eight received no concentrated feeds. Also during that time, the researchers infected all the mares with roundworms to investigate their ability to fight off infection with the different nutritional inputs. The team weighed the mares and foals regularly and evaluated their body condition and parasite loads throughout the study.

The researchers found that, although both groups of mares spent exactly the same amount of time grazing (15 hours a day on average), pasture-only mares ingested 12% more grass during the entire study period than the complementary feed group. Collas said the pasture-only mares were probably more efficient with their grazing, taking in more grass per mouthful and swallowing faster.

Both groups of broodmares maintained their weight relatively well until the end of the study, at which point both groups lost weight. In fact, the complementary feed group of mares actually lost more weight than the pasture-only mares, Collas said. Weight loss at the end of the study could be due to a variety of factors, including reduced available forage on the pasture (however, no measure of intake was available at the end of the study) and increased parasite loads.

Meanwhile, neither group appeared more effective than the other in fighting off parasite infection, Collas said.

As for the foals, both groups followed the same growth curves, with the pasture-only group’s foals gaining height and weight in the same pattern as the complemented group’s foals, Collas said.

“In our pasture conditions, the absence of complementary feed did not penalize foal growth or the conservation of mares’ body reserves, compared to an energy complement designed to meet 60% of lactation needs,” said Collas. “The strong ability of mares to ingest green forages explains this result, which is consistent with previous studies conducted with conserved forages at INRA.”

Additional studies in more limiting pasture conditions (such as different amounts of grass available) are under way to help develop specific feeding recommendations for breeders, Collas said.

About the Author

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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